Add test to do sanity checking of core picker and default core prefs

src/BizHawk.Client.Common/config/Config.cs

@@ -11,7 +11,28 @@ namespace BizHawk.Client.Common
 	public class Config
 	{
 		public static string ControlDefaultPath => Path.Combine(PathUtils.ExeDirectoryPath, "defctrl.json");
-		
+
+		/// <remarks>
+		/// <c>AppliesTo[0]</c> is used as the group label, and
+		/// <c>Config.PreferredCores[AppliesTo[0]]</c> (lookup on global <see cref="Config"/> instance) determines the currently selected option.
+		/// The tuples' order determines the order of menu items.
+		/// </remarks>
+		public static readonly IReadOnlyList<(string[] AppliesTo, string[] CoreNames)> CorePickerUIData = new List<(string[], string[])>
+		{
+			(new[] { "NES" },
+				new[] { CoreNames.QuickNes, CoreNames.NesHawk, CoreNames.SubNesHawk }),
+			(new[] { "SNES" },
+				new[] { CoreNames.Faust, CoreNames.Snes9X, CoreNames.Bsnes }),
+			(new[] { "SGB" },
+				new[] { CoreNames.SameBoy, CoreNames.Bsnes }),
+			(new[] { "GB", "GBC" },
+				new[] { CoreNames.Gambatte, CoreNames.GbHawk, CoreNames.SubGbHawk }),
+			(new[] { "DGB" },
+				new[] { CoreNames.DualGambatte, CoreNames.GBHawkLink }),
+			(new[] { "PCE", "PCECD", "SGX" },
+				new[] { CoreNames.TurboNyma, CoreNames.HyperNyma, CoreNames.PceHawk })
+		};
+
 		public static string DefaultIniPath { get; private set; } = Path.Combine(PathUtils.ExeDirectoryPath, "config.ini");
 
 		// Shenanigans

src/BizHawk.Client.EmuHawk/MainForm.cs

@@ -44,21 +44,11 @@ namespace BizHawk.Client.EmuHawk
 {
 	public partial class MainForm : FormBase, IDialogParent, IMainFormForApi, IMainFormForConfig, IMainFormForTools
 	{
-		/// <remarks><c>AppliesTo[0]</c> is used as the group label, and <c>Config.PreferredCores[AppliesTo[0]]</c> determines the currently selected option</remarks>
-		private static readonly IReadOnlyCollection<(string[] AppliesTo, string[] CoreNames)> CoreData = new List<(string[], string[])> {
-			(new[] { "NES" }, new[] { CoreNames.QuickNes, CoreNames.NesHawk, CoreNames.SubNesHawk }),
-			(new[] { "SNES" }, new[] { CoreNames.Faust, CoreNames.Snes9X, CoreNames.Bsnes }),
-			(new[] { "SGB" }, new[] { CoreNames.SameBoy, CoreNames.Bsnes }),
-			(new[] { "GB", "GBC" }, new[] { CoreNames.Gambatte, CoreNames.GbHawk, CoreNames.SubGbHawk }),
-			(new[] { "DGB" }, new[] { CoreNames.DualGambatte, CoreNames.GBHawkLink }),
-			(new[] { "PCE", "PCECD", "SGX" }, new[] { CoreNames.TurboNyma, CoreNames.HyperNyma, CoreNames.PceHawk })
-		};
-
 		private void MainForm_Load(object sender, EventArgs e)
 		{
 			SetWindowText();
 
-			foreach (var (appliesTo, coreNames) in CoreData)
+			foreach (var (appliesTo, coreNames) in Config.CorePickerUIData)
 			{
 				var groupLabel = appliesTo[0];
 				var submenu = new ToolStripMenuItem { Text = groupLabel };

src/BizHawk.Emulation.Cores/CoreInventory.cs

@@ -14,6 +14,9 @@ namespace BizHawk.Emulation.Cores
 	{
 		private readonly Dictionary<string, List<Core>> _systems = new Dictionary<string, List<Core>>();
 
+		/// <summary>keys are system IDs; values are core/ctor info for all that system's cores</summary>
+		public IReadOnlyDictionary<string, List<Core>> AllCores => _systems;
+
 		public readonly IReadOnlyCollection<Core> SystemsFlat;
 
 		public class Core

src/BizHawk.Tests/Client.EmuHawk/CorePickerStabilityTests.cs

@@ -0,0 +1,65 @@
+using System.Collections.Generic;
+using System.Linq;
+
+using BizHawk.Client.Common;
+using BizHawk.Emulation.Cores;
+
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace BizHawk.Tests.Client.EmuHawk
+{
+	[TestClass]
+	public sealed class CorePickerStabilityTests
+	{
+		private static readonly IReadOnlyDictionary<string, string> DefaultCorePrefDict = new Config().PreferredCores;
+
+		[TestMethod]
+		public void AssertAllChoicesInMenu()
+		{
+			var multiCoreSystems = CoreInventory.Instance.AllCores.Where(kvp => kvp.Value.Count != 1)
+				.Select(kvp => kvp.Key)
+				.ToHashSet();
+			foreach (var sysID in DefaultCorePrefDict.Keys)
+			{
+				Assert.IsTrue(multiCoreSystems.Contains(sysID), $"a default core preference exists for {sysID} but that system doesn't have alternate cores");
+			}
+			foreach (var (appliesTo, _) in Config.CorePickerUIData)
+			{
+				Assert.IsTrue(
+					appliesTo.Any(multiCoreSystems.Contains),
+					$"core picker has submenu for {appliesTo[0]} ({string.Join('/', appliesTo)}), but {(appliesTo.Length == 1 ? "that system doesn't have" : "none of those systems have")} alternate cores");
+			}
+		}
+
+		[TestMethod]
+		public void AssertNoMissingCores()
+		{
+			var allCoreNames = CoreInventory.Instance.SystemsFlat.Select(coreInfo => coreInfo.Name).ToHashSet();
+			foreach (var kvp in DefaultCorePrefDict)
+			{
+				Assert.IsTrue(allCoreNames.Contains(kvp.Value), $"default core preference for {kvp.Key} is \"{kvp.Value}\", which doesn't exist");
+			}
+			foreach (var (appliesTo, coreNames) in Config.CorePickerUIData) foreach (var coreName in coreNames)
+			{
+				Assert.IsTrue(allCoreNames.Contains(coreName), $"core picker includes nonexistant core \"{coreName}\" under {appliesTo[0]} group");
+			}
+		}
+
+		/// <remarks>this really shouldn't be necessary</remarks>
+		[TestMethod]
+		public void AssertNoMissingSystems()
+		{
+			var allSysIDs = CoreInventory.Instance.AllCores.Keys.ToHashSet();
+#if false // already covered by AssertAllChoicesInMenu
+			foreach (var sysID in DefaultCorePrefDict.Keys)
+			{
+				Assert.IsTrue(allSysIDs.Contains(sysID), $"a default core preference exists for {sysID}, which isn't emulated by any core");
+			}
+#endif
+			foreach (var (appliesTo, _) in Config.CorePickerUIData) foreach (var sysID in appliesTo)
+			{
+				Assert.IsTrue(allSysIDs.Contains(sysID), $"core picker has choices for {sysID}, which isn't emulated by any core");
+			}
+		}
+	}
+}